Under drive pullys.

[tomtom72]

Jerry, No way partner do I take your contribution to this topic as any thing other than trying to get to the bottom of this issue.

I am fairly short on facts on this matter.....you know all about the famed post card & the sum of my info...

Okay, so it's not an accurate statement that at some point in our rpm band that the by-pass excludes the rad core? I got that impression from THOTB where they talked about the prep for the car & the throttle stop & rear gear, etc yielding a cruising speed below a certain rpm to avoid the by-pass, >5600 rpms is my recollection?

I do know that I saw a thread over at CF where one of the aftermarket makers freely admitted that our gpm flow ( which he thought to be excessively high ) could cause a ballooning of the tubes if left unrestricted because it was so far & away beyond any common domestic water pump's gpm flow.

Tyler had a solution ( proly the same as yours & LPE's ) where he used a restriction in the by-pass outlet of the housing, a cut spring stat I think with holes drilled like yours, and one of the really high end aftermarket radiators. If I understood correctly this all yielded less by-pass or moved the by-pass up in the rpm range.......I don't remember which....so you could get flow thru the rad at high rpms like during an open road race situation. I would figure in an ORR you're spending a great deal of time above 5k rpms?... not me but a good driver would be, no?

Next year at the Gathering I'm going to ask to have this whole thing explained if we have a seminar where Marc or Mr. McLellan is available to lend their knowledge.

My simple answer is to keep the by-pass as is, redesign the impeller to lower the flow rate......(Yea, right, simple!...ignorance is bliss sometimes).... and use a high end radiator.

Tom

[A26B]

Imagine the bypass as a non positive valve that varies the radiator bypass flow potential according to pump output pressure, but never shuts off flow to the radiator. Therefore, it is NOT correct that the bypass excludes the radiator core. It simply opens up another flow passage that bypasses the radiator. Whatever volume of coolant that still flows through the radiator will help cooling.

[A26B]

My simple answer is to keep the by-pass as is, redesign the impeller to lower the flow rate......(Yea, right, simple!...ignorance is bliss sometimes).... and use a high end radiator.

Well, if you reduce the flow rate by modifying the impeller, all you've done is reduce the amount of coolant that flows through the radiator at all rpm's under the bypass opening rpm.

By Hib Halverson: Two cars were built and tested during the fall and winter. The Mobil/EDS/Goodyear Corvette chassis were stock except for: no side mirrors, lowered front end, reinforced front air dams fitted with ultrasonic "anti-animal" whistles, no rear antiroll bars, transmission and differential oil coolers, 3.07:1 axle ratio on the ZR-1 and a 2.72:1 for the L98 car and 25.5x12.0-17 Special Radial tires that Goodyear built for this effort. Replacing the passenger seats were EDS telemetry systems operated by GM's Service Technology Group. The cars were heavy carrying a roll cage, other safety equipment and 48 gal. fuel cells. As FIA rules require "non-consumable" spare parts (brake rotor, radiator hose, alternator, etc.) to be carried in the car, 300 lbs. of spares were in two suitcases lashed to the cages' rear tubes. Replacements had to come from this stock and, if a failure was such that a car could not get back to the pits; the driver, working alone, had to fix the car. Ab's ghost to smiled even more.

The LT-5 was picked right off Mercury Marine's Stillwater, Oklahoma assembly line. Less catalytic converters and mufflers, but with revised engine management software, its horsepower was about 405. Tests had shown speed necessary to reset The 24 would come at 5500 rpm in fifth gear so the engine had a stop at 70% throttle.

Note: no mention of the rpm limit having been established due to the coolant bypass system.

LT5 Water pump flow rate: 12 gpm @ idle 85 gpm @ 7,000 rpm

I'm still searching for some "hard" data regarding the thermostat bypass valve operation specs.

[4-cam]

I hope this article explains how flow rates affect heat transfer.Its not from the automotive industry but does explain flow characteristics. Basically to little flow will lower heat transfer in the engine block and radiator as it will not create enough turbulence.Then as the flow increases and you have turbulent flow thru the radiator and block heat transfer is optimized. I you have to much flow the heat transfer rate will start to drop off again.


TURBULENT AND LAMINAR FLOW

[IMG]file:///C:/Users/Darby/AppData/Local/Temp/msohtml1/01/clip_image001.jpg[/IMG]Heat transfer is the ability to pass heat between a warmer object to a cooler object.
In plastics processing, heat transfer is used to heat or cool objects such as molds, rolls, vessels, heat exchangers and others.
These objects have a system of channels 'molded' into their bodies. Water (or some other fluid) is pumped through these channels in an effort to heat or cool these bodies.
When fluid is pumped through these channels, it can develop two basic characteristics: laminar or turbulent flow.
Laminar Flow is defined as fluid gliding through a channel in smooth layers, where the innermost layer flows at a higher rate than the outermost.
Turbulent Flow is characterized by turbulence, where fluid does not flow in smooth layers but is agitated.
Heat transfer occurs at the channel wall. Laminar flow develops an insulating blanket around the channel wall and restricts heat transfer. Conversely, turbulent flow, due to the agitation factor, develops no insulating blanket and heat is transferred very rapidly.
Turbulent flow occurs when the velocity in a given water channel is high. Although too much velocity can cause erosion. Many equipment manufacturers publish specific flow and supply pressure requirements to achieve turbulent flow. Advantage temperature control units, portable and central liquid chillers, and pump tank stations are designed to generate turbulent flow.

[HAWAIIZR-1]

Originally Posted by GOLDCYLON

Craig are you also running the ATI super balancer on your car? Any clearance issue with these mods? I called SRP today and emailed them this morning I have not heard a peep yet

Daryll,

I have the stock balancer on my motor and was able to get the 3 piece set at the time. I thought about the ATI at the time, but was worried about issues as I have enough of those already. I will say that I did not find any noticeably changes to cooling or charging system with the under drive pulley set.

[GOLDCYLON]

Originally Posted by HAWAIIZR-1

Daryll,

I have the stock balancer on my motor and was able to get the 3 piece set at the time. I thought about the ATI at the time, but was worried about issues as I have enough of those already. I will say that I did not find any noticeably changes to cooling or charging system with the under drive pulley set.

Thanks Craig good to know. The 2 piece is NLA with no future stock forseeable according to Ron. He left me a voice mail

[HAWAIIZR-1]

Originally Posted by GOLDCYLON

Thanks Craig good to know. The 2 piece is NLA with no future stock forseeable according to Ron. He left me a voice mail

Sorry to hear that and I see they list separately the power steering and the water pump, the only thing missing is the alternator pulley. I don't think there was a size difference with that part, but aluminum and lightweight if I remember correctly.

Calling on Carter...........How about some under drive pulleys?

[tomtom72]

http://forums.*************.com/c4-z...-included.html

This is a link to a thread, from a long time ago, over at the other place. I book marked it so I could try to learn what our by-pass system does. I thought I'd share it with the members here.

Jerry, I think I get what I was miss understanding. I should have realized that the radiator used for all C4's is matched to a standard 350 sbc w/p's gpm flow and not our Lotus spec'ed pumps. Also, I forgot that the by-pass serves to pre-heat our stats so they can open? Anyway, the stock rad can't flow what our LT5 pumps put out so they cause the coolant flow to back up. If it wasn't for the by-pass the rad would blow the side tanks off....not a pleasant thought....even if the whole rad was aluminum, if the flow allowed by the tube diameter wasn't enough there would still be a restriction and the tubes would proly blow out.

Thank you for your patience with my rather dense grey matter.


Tom

never mind about the link, I forgot. /c4-zr-1-discussion/259664-thermostat-cooling-discussion-pic-included.html[/url]